A study published Wednesday links Medtronic Inc.'s Infuse spinal graft to a condition that can cause infertility in men.

The clinical study said men who were treated with Infuse were more likely to develop retrograde ejaculation than men treated with other bone grafts. Retrograde ejaculation is a condition in which semen goes into the bladder after ejaculation instead of leaving the body through the urethra. It's not harmful, but it can cause infertility.

The results appeared Wednesday in the online version of The Spine Journal, a publication of the North American Spine Society. Medtronic did not immediately respond to a request for comment.

Infuse contains a genetically engineered protein that can stimulate bone growth. It is used in spinal, oral, and dental graft procedures, and is an alternative to procedures like autologous grafting, where bone is taken from elsewhere in the patient's body. Those procedures can cause lasting pain.

The study by Stanford University researchers included about 230 men who had a common type of spinal fusion procedure. Out of 69 men who received an Infuse graft, five experienced retrograde ejaculation. Out of 174 patients who were treated with other bone grafts, only one experienced retrograde ejaculation. Three of the six cases cleared up within a year, including the one in the man who did not receive an Infuse graft.

Infuse has been linked to a variety of other complications since it was approved. Medtronic's website lists "sexual dysfunction" as one possible risk associated with spinal surgery but does not connect it specifically to Infuse.

In afternoon trading, Medtronic shares lost 66 cents to $40.22.